[R12.1.3] Possible reason for ICM starting late after adstrtal.sh execute?

Hi, experts

I got a temporary issue with ICM :

the ICM log start to wrote 8 minutes after adstrtal.sh execute.

Normally, the ICM log starts right after adstrtal.sh.

Only below message wrote during the 8 min.

==START==

========================================================================

Starting XXXX_XXXX@XXXX Internal Concurrent Manager -- shell process ID 123456789

          logfile=/<path>/logs/appl/conc/log/XXXX_XXXX.mgr

          PRINTER=noprint

           mailto=XXXX

          restart=N

             diag=N

            sleep=30

             pmon=4

           quesiz=1

          Reviver is ENABLED

==END==

Questions:

I want to know the possible reason of this issue:

1. What could be possible reason for ICM starts late 8 min?

2. Any log/method could confirm what happened at that time?